Recovered coupler purification process



United States Patent 3 458 574 RECOVERED conrrnn rnnrarcAnoN PRGtZESS Courtenay D. Anselm and Kenneth R. Reitz, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, NY a corporation of New iersey No Drawing. Filed Feb. 21, 1966, Ser. No. 528,767 Int. Cl. 603s 7/32; (39% 103/02 US. Cl. 269-562 8 Claims ABSTRAQT @F THE DISCLOSURE Dye-forming coupler recovered from photographic color developer solution is purified by contacting the impure coupler in admixture with water with an organic solvent comprising an acylating agent so that the acylating agent reacts with the water to generate heat and bring about solution of the coupler and the impurities, whereupon the coupler is recovered in purified form by recrystallization from the solution. Where the coupler has an acylarnido group substituent, the acylating agent also acts to convert to coupler any amine derivative formed by alkaline hydrolysis of the acylamido group in the developer solution.

This invention relates to color photography and more particularly to photographic color developer solutions and a novel method for recovering color forming coupler in pure form from used and/or exhausted color developer solutions.

Color developing solutions are used in the processing of exposed photographic elements for color photography in order to produce the dye images that form the color picture in the processed element. In the processing of three color subtractive type photographic elements, the final picture is usually made by the formation of a cyan dye image, a yellow dye image and a magenta dye image in superposed relationship. The cyan dye image development is accomplished with an alkaline developer solution which contains a color developer and a cyan-forming coupler which is usually a phenolic or naphtholic type coupler. Where exposed silver halide in the cyan image layer is developed to silver, color developer is oxidized to a compound that couples with the cyan-forming coupler present to form a nondilfusing dye image. The yellow dye image development is accomplished with an alkaline developer solution containing a color developer and a yellow dye-forming coupler. Similarly, the magenta dye image is developed with an alkaline developer containing a color developer and a magenta dye-forming coupler. Usually, acylacetamide type couplers are used in yellow dyeforming developers and a Z-pyrazolin-S-one or a coumarone type coupler is used in the magenta dye-forming developer. Each of these color-forming couplers have a reactive hydrogen on a methylene group that is adjacent to a keto group, or a reactive hydrogen atom on a methine group that is ortho to or para to a hydroxy group on an aromatic ring.

In addition to the color developer and color-forming coupler, the alkaline developer solution usually contains other constituents such as potassium bromide, sodium sulfite, sodium carbonate, and other materials in order to give a developed image having the desired sensitometric characteristics (that is, relationship between exposure and resulting image density).

Commercial color processing is usually done on a continuous basis, in which a continuous flow of color film is processed through the various processing solutions including the color developers in a processing machine. Since the concentrations of the chemicals in the developer solutions (as well as other solutions) must be maintained within certain ranges to give good sensitometric results,

ice

it is common practice to replenish the various developers by a controlled flow of the appropriate replenisher solutions. In this way, the proper equilibria are maintained to give color development of optimum quality. Replenishment of the developer solution tanks in the processing machine results in displacement of used developer solution which is discarded.

Alternatively, when relatively small amounts of film are to be processed, a batch process may be used in which developer solutions are used untilexhausted, then replaced with fresh developer for another batch of film.

In each type of processing, the exhausted or used developer solution still contains substantial concentrations of the color-forming coupler. Because of the relatively high cost of the coupler compounds, it is advantageous to recover them for reuse in fresh developer solution.

It is known to precipitate the acid color-forming coupler compounds from aqueous alkaline color developer solutions containing them by acidification with mineral acids, such as hydrochloric acid, sulfuric acid, etc., or by dissolving carbon dioxide in the color developer solution. The precipitated coupler is then removed from the solution by filtration or by centrifuging, washed and dried. The couplers produced by this process have been used in making fresh color developer solution. However, because of impurities, especially certain photographically active impurities present in the recovered coupler, it has often not been possible to use the recovered coupler unless blended with at least or more of freshly synthesized coupler. Because of variations in the photographic eflects of various blends of recovered and freshly synthesized couplers, it has frequently been difficult to maintain the desired control over the color photographic processusing these materials. Processes are desired which will produce a coupler in a sufiiciently purified form so that it can be used in place of freshly synthesized coupler without blending with fresh coupler.

One object of our invention is to provide a novel process for easily and efficiently purifying acid dye-forming couplers recovered from spent (used and/or exhausted) aqueous alkaline color developer solutions so that the purified recovered coupler is photographically indistinguishable from freshly synthesized coupler.

Another object of our invention is to provide a novel process for contacting impure coupler recovered from spent aqueous alkaline color developer solutions with an brganic solvent comprising an acylating agent so that sufiicient heat is produced to dissolve the impurities and a substantial amount of the coupler, as Well as acylating any of the amine derivative of the said coupler which may have been further produced by alkaline hydrolysis of the acylamido groupon the said coupler, followed by recrystallization of the coupler and removal of substantially all of the dissolved impurities leaving pure coupler.

Another object of our invention is to provide a novel process in which the deacylated coupler in impure recovered coupler is reconverted to the coupler and the necessary heat for recrystallization is simultaneously supplied, by contacting the impure coupler in the presence of water with an acylating agent, thus reforming coupler from an inert impurity which would otherwise be lost and eliminating the need for expensive equipment for supplying heat needed for recrystallization from external sources.

Still another object of our invention is to provide a novel process for repurifying dried impure coupler recovered by prior art methods so that the unsatisfactory coupler can be purified sufficiently so that it can be used in place of freshly synthesized coupler.

Still other objects of our invention will be obvious from consideration of the following specification and claims.

These and other objects are accomplished according to our invention by (1) contacting a mixture of impure acid dye-forming coupler that is free of substituents that will react with acylating agents and preferably bearing an acylamido group substituent, and water with an organic solvent comprising sufficient acylating agent to convert any amine derivative of said coupler (produced by alkaline hydrolysis of the said acylamido group) to the said coupler and to react with the water present to elevate the temperature of the mixture sufficiently to effect solution of impurities and a substantial amount of the coupler and (2) recrystallizing the coupler by (a) allowing the hot mixture from step 1 to cool suificiently for the dissolved coupler to recrystallize leaving the impurities in solution and/or by (b) adding water, and (3) extracting substantially all of the solution containing the impurities from the coupler leaving wet purified coupler which, when dried, can be used in place of newly synthesized coupler in the color developer solutions.

Our process is used advantageously to easily and effectively convert impure coupler recovered from spent color developer solutions by acidification methods so that the purified coupler is substantially free from both inactive and photographically active impurities and can be used weight by Weight in place of freshly synthesized coupler, producing uniformly high-quality photographic results. A very important feature of our method is the reformation of coupler from the amine derivative of the coupler (formed by alkaline hydrolysis of the acylamido group on couplers in used color developer solutions). The reformation of the coupler from the photographically inactive amine derivative makes available for recovery from approximately 3 to 10% of additional coupler which would otherwise be lost and could even be a very unwanted diluent in the recovered coupler material. This additional amount of coupler provides a saving which may pay for the cost of recovering the coupler.

Our process provides a method in which a high concentration of organic solvent is obtained in the wet impure coupler precipitate with a relatively small volume of organic solvent. Since the acylating agent reacts exothermically with water present, all of the heat necessary for recrystallization is supplied by this reaction. This eliminates the need for an external source of heat as well as expensive heat exchanging equipment which would otherwise be necessary. The maximum temperature of the reaction is easily controlled by the choice of the ratio of damp coupler and the organic solvent used.

Our process is used to advantage in purifying any aqueous alkali-soluble acid color-forming coupler used in color developer solutions for photographic color processing provided that the coupler is free of substituents (e.g., amino, alkylamino, hydroxyalkylamino, etc.), that react with acylating agents, and preferably couplers that have an acylamido group substituent e.g., acetamido, propionamido, butyrylamido, etc. Included among typical preferred couplers that are recovered from color developer solutions and purified according to our process are the following:

2-acetamido-5-methylphenol 7-acetamido-2-naphthol 5-acetamido-2carbethoxyphenol 5 -butyrylamido-2-carbethoxyphenol 5 -propionylamido-2-phenylcarb amyl phenol 5-acetarnido-2-phenylcarbamy1phenol 2,5 -diacetamidophenol 2- (p-acetamido-,8-phenylethyl -1-hydroxynaphthamide 2-(o-acetarnido-[i-phenylethyl) -1-hydroxynaphthamide 1-phenyl-3 -valerylamido-2-pyrazolin-5-one 1-phenyl-3-propionylamido -2-pyrazolin-5 -one 1-pheny1-3-acetylamido-2-pyrazolin-5 -one 1- (p-cyanophenyl) -3 -acetamido-2-pyrazolin-S-one 1-( 2,4, 6-trichlorophenyl -3 -acetamido-2-pyrazolin-5 -one 1- (p-acetamidophenyl -3-anilino-2-pyrazolin-5-one These and other couplers, well known in the art, are purified to advantage according to our process.

As has been indicated previously, acid color-forming coupler is precipitated from the aqueous alkaline color developer solution by acidifying the solution with a mineral acid or preferably by bubbling carbon dioxide gas throughout the solution as described in Anselm, US. Patent 3,201,412, issued Aug. 17, 1965. The solution is then removed from precipitated coupler by any suitable means, such as by filtration, centrifuging, etc. The Wet coupler in the filter cake from the filtration or centrifuging contains in the range from about 25 to about 75% water by weight.

In processes used previously, the filter cake was dried. In our process the wet impure recovered coupler (filter cake) containing at least about 25% water is contacted with an organic solvent comprising an acylating agent with or without an organic acid, e.g., acetic acid, pro pionic acid, butyric acid, etc. It is advantageous to treat the wet coupler in a tank provided with a suitable means for intimate mixing during and after the addition of the organic solvent. A vent pipe adjacent to the top of the tank with sufficient air flow is used to advantage to remove solvent fumes.

'If it is desired to purify recovered coupler that has already been dried, the dry material is moistened by adding about 200% by weight of water before treating with the organic solvent(s).

The acylating agents used to advantage according to our invention include organic acid anhydrides, e.g., acetic anhydride, propionic anhydride, butyric anhydride, etc., organic acid halides, e.g., acetyl chloride, propionyl chloride, butyryl chloride, acetyl bromide, propionyl bromide, etc. The acylating agent used is chosen so that the desired acylamido group will be reformed on the amine derivative of the coupler. The organic acid anhydrides are usually the preferred acylating agents in our process. The amount of acylating agent used may be varied considerably and will depend upon the amount of water in the damp impure recovered coupler being treated, the amount of amine to be reconverted to coupler, the maximum temperature desired in the reacting mixture, etc. The mole ratio of acylating agent to water in the damp impure recovered coupler can advantageously be in the range from about 1:1 to about 1:8 with a range of from about 1:3 to about 1:4 being preferred. We have found a mole ratio of 1:4 to be excellent. In the preferred ratios there is a large excess of water so the amount of acylating agent used determines the amount of heat produced and the maximum amount of temperature rise. The temperatures used to advantage are in the range of from about F. to about 260 F., preferably in the range from about 180 F. to about 220 F.

The minimum total solvent that is used advantageously is that which produces a slurry of coupler in the solvent that is thin enough to be stirred. This will depend upon the characteristics of the particular coupler involved. When the acylating agent does not provide the minimum solvent volume desired, solvents such as acetic acid, propionic acid, etc. are used to advantage to give the desired volume.

After completion of the reaction of acylating agent with the amine derivative of the coupler and water, the reaction mixture is allowed to cool to room temperature or sufliciently to cause recrystallization of the coupler which dissolved during the reaction step when heat was involved. Although it is not necessary to add water to the cooling reaction mixtures, it is advantageous to add water having a volume of from about one-half to about 10 times the volume of the organic solvents, any time after the maximum temperature has been reached. The addition of water gives a thinner slurry and will aid in recrystallization of the dissolved coupler.

When coupler recrystallization is completed, solvent is removed by suitable means e.g., filtration, centrifuging,

etc. and the filter cake dried or water Washed, filtered (or centrifuged) and then dried. The dried coupler is sufficiently pure for use in making color developer solutions without blending it with freshly synthesized coupler.

The following typical examples will still further illustrate our invention.

Example 1 Cyan color developer collected from the overflow of the cyan color developer tank in a color processing machine was acidified to precipitate the couple 2-(0- acetamido-fi-phenylethyl) 1 hydroxynaphthamide. The slurry was centrifuged to remove the solution leaving recovered damp coupler containing about 70% by weight water. Six kg. of this damp coupler was placed in a tank and stirred while a mixture of 5 liters of acetic anhydride and 4 liters of acetic acid were added. A maximum temtemperature of 196 F. was obtained in about 50 minutes. When the temperature receded to about 180 F., 6 liters of water were added, stirred and the mixture was allowed to cool to room temperature. The cooled mixture was filtered through filter paper and the coupler filter cake was washed twice with about 5 liters of water each time. The damp coupler was spread in glass trays and dried by a combination of hood-drying for 5 days and oven-drying at 212 F. for 32 hours. Based on the dry weight of 400 grams of the same damp coupler used for purification, a 94% yield was obtained.

Four photographic tests showed that although the unpurified, recovered coupler starting material was not acceptable, our purified coupler was indistinguishable from freshly synthesized 2-(o-acetamido-B-phenylethyl)-l-hydroxynaphthamide.

Example 2 Six kg. of the recovered damp coupler containing about 70% by weight water obtained by centrifuging acidified cyan developer solution was stirred in a tank while 5 liters of acetic anhydride and 2 liters of acetic acid were added. The slurry was too thick to stir well and another liter of acetic acid was added. A maximum temperature of 210 F. was attained. When the temperature dropped to 205 F., 6 liters of water were added, stirred, and the mixture allowed to cool at room temperature. Some of the batch was collected in a small centrifuge, washed with hot water and dried at 212 F. The rest of the batch was filtered, washed and dried as in Example 1.

Eight photographic tests showed that although the starting material was not acceptable, the purified material from the centrifuge and filter was indistinguishable from freshly synthesized coupler.

Example 3 Example 2 was repeated excepting that the 3 liters of acetic acid were all added with the acetic anhydride. A maximum temperature of 200 F. was obtained with stirring being continued until the temperature receded to 150 F., then 5 liters of water were added, stirred 10 minutes and the mixture allowed to cool to room temperature. The cooled material was filtered, washed, and dried as in Example 1. An 88% yield was obtained. Four photographic tests showed that although starting material was unacceptable, the purified material was indistinguishable from fresh coupler.

Similar results are obtained when no water is added to the cooling reaction mixture in the above examples, although the percent yield of coupler may be lower. Results similar to those obtained in the preceding examples are obtained when other of the illustrative couplers are used in place of 2-(o-acetamido-;8-phenylethyl)-l-hydroxynaphthamide, and other illustrative acylating agents and acids are used in place of acetic anhydride and acetic acid.

Example 4 Similar results are obtained when Example 1 is repeated in which a cyan developer containing the cyan coupler 5-propionylamide-Z-phenyl carbamylphenol is used in place of the color developer solution of Example 1. In this process propionyl chloride is used in place of acetic anhydride.

Example 5 Similar results are obtained when Example 1 is repeated in which a magenta color developer solution containing the magenta coupler l-(p-acetamidophenyl)-3- anilino-2-pyrazolin-5-one is used in place of the cyan color developer in Example 1.

Our process is used to advantage in purifying any aqueous alkali-soluble, acid, color-forming coupler used in color developer solutions for photographic color processing providing that the coupler is free of substituents, e.g., amino, alkamino, hydroxyalkyl, etc. that react with acylating agents and preferably couplers that have an acylamido group substituent. Our process produces a coupler which is photographically indistinguishable from freshly synthesized couplers when used in making color developer solutions. The reaction used not only reforms coupler from photographically inert coupler derivatives formed by alkaline hydrolysis of the coupler in spent color developer solutions, but furnishes all of the heat required for recrystallization of the coupler. All of these advantages provide a substantial technical advance through the use of our process.

The invention has been described in detail with particular reference to preferred embodiments thereof but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A process for purifying impure acid dye-forming coupler that has been recovered from aqueous alkaline photographic color-forming developer solution by precipitation with a mineral acid or carbon dioxide, said coupler bearing an alkanoylamido group substituent and being free of substituents that react with acylating agents and said impure coupler containing as one impurity the amine derivative of said coupler, said amine derivative having been formed in said color developer solution as a result of alkaline hydrolysis of said alkanoylamido group; said process comprising the steps of (l) contacting a mixture comprising said impure coupler and water wherein the water is at least about 25 percent by weight of said mixture with an organic solvent comprising a sufficient amount of an acylating agent, selected from the group consisting of the anhydride and the halide of the alkanoic acid corresponding to the alkanoyl radical of said alkanoylamido group, to convert said amine derivative to said coupler and to react with the water present to elevate the temperature of the mixture formed to within the range from about F. to about 250 F. to thereby effect solution of the impurities and of a substantial amount of said coupler.

(2) recrystallizing said dissolved coupler in the mixture from step (1) by cooling or by diluting with water in an amount equal to from about one-half to about ten times the volume of organic solvent utilized in step (1) to thereby leave the impurities in solution, and

(3) extracting from the mixture from step (2) substantially all of the solution containing the impurities to thereby leave wet purified coupler which, when dried, can be used in place of newly synthesized coupler in color developer solutions.

2. The process as described in claim 1 wherein said alkanoylamido group contains 2 to 5 carbon atoms.

3. The process as described in claim 1 wherein said alkanoylamido group is an acetamido group and said acylating agent is acetic anhydride.

4. The process as described in claim 1 wherein the wet purified coupler of step (3) is washed with water prior to drying.

5. The process as described in claim 1 wherein said alkanoylamido group is an acetamido group, said acylating agent is acetic anhydride, and said organic solvent is acetic acid.

6. The process as described in claim :1 wherein said coupler is 2-(o-acetamido[3-phenylethyl-l-hydroxy naphthamide and said amine derivative is 2-(o-amino-B- phenylethyD-l-hydroxy naphthamide.

7. A process for recovering aqueous-alkali-soluble acid dye-forming coupler from a photographic color-forming developer solution, said coupler bearing an alkanoylamido group substituent and being free of substituents that react with acylating agents and said developer solution comprising water, an alkali, a primary aromatic amino color developing agent, a water-soluble alkali metal salt of said coupler, and a water-soluble alakli metal salt of the amine derivative formed by alkaline hydrolysis of the alkanoylamido group on said coupler; said process comprising the steps of:

(l) acidifying said developer solution by addition of a member selected from the group consisting of mineral acids and carbon dioxide to thereby form a precipitate comprising substantially all of said coupler and substantially all of said amine derivative,

(2) recovering said precipitate, washing said precipitate with water, and forming therefrom a mixture with water wherein the water is at least about 25 percent by weight of said mixture.

(3) contacting said mixture with an organic solvent comprising a sufiicient amount of an acylating agent, selected from the group consisting of the anhydride and the halide of the alkanoic acid corresponding to the alkanoyl radical of said alkanoylamido group, to convert said amine derivative to said coupler and to react with the water present to elevate the temperture of the mixture formed to within the range from about F. to about 250 F. to thereby effect solution of the impurities and of a substantial amount of said coupler,

(4) recrystallizing said dissolved coupler in the mixture from step (3) by cooling or by diluting with water in an amount equal to from about one-half to about ten times the volume of organic solvent utilized in step (3) to thereby leave the impurities in solution, and

(5) extracting from the mixture from step (4) substantially all of the solution containing the impurities to thereby leave wet purified coupler which, when dried, can be used in place of newly synthesized coupler in color developer solutions.

-8. The process as described in claim 7 wherein said coupler is 2-(o-acetamido-B-phenylethyl) 1 hydroxy naphthamide, said amine derivative is 2-(o-amino-B- phenylethyD-l-hydroxy naphthamide, said acylating agent is acetic anhydride, and said organic solvent is acetic acid.

No references cited HENRY R. NILES, Primary Examiner HARRY I. MOATZ, Assistant Examiner US. Cl. X.R. 

